The Pressure Testing Methods for Shutoff Valve
The opening and closing mechanism of shut-off valve is to rely on the pressure of valve stem to make the sealing surface of the valve flap and the sealing surface of the valve seat tightly fit and prevent medium from flowing.
Sanitary shut-off valve only allows one-way flow of the medium. The installation is directional. The structural length of it is longer than that of gate valve. Meanwhile, the fluid resistance is large. The sealing reliability is not good for long-time running. There’re three types of shut-off valve: straight-through, right angle, and straight-flow oblique type.
The use of shut-off valve:
Shut-off valve plays the important role of cutting off and throttling the medium in the pipeline. Shut-off valve is a type of valve that is very widely used. The reason why it is so popular is because the friction between sealing surfaces is small during the opening and closing process. It is durable and the height of opening is not high. The manufacture and maintenance are easy. It is not only suitable for medium- and low-pressure, but also suitable for high pressure.
For strength test, we usually put assembled valves in the pressure testing rack, open the valve flap, pour in the medium to the specified value to see if there is leakage at the valve body and valve cover. The strength test can also be conducted individually.
For sealing performance test, the valve stem of shut-off valve is in a vertical state. When the valve flap opens, the medium is introduced to the specified value from the bottom of the valve flap. Check the stuffing and gasket. Close the valve flap after the valve is qualified, and open the other end to check if there is leakage.
If both the strength test and sealing performance test need to be conducted, we can first conduct the strength test, then lower the pressure to the specified value of the sealing performance test. Check the stuffing and gasket. Then close the valve flap, and open the outlet to check if there is leakage at the sealing surface.